Hot alternator

[motorhead446]

I have a power master mini alternator that gets hot when engine is not running. It's a one wire design. Nothing else is on like electric fan or similar. After turning on master disconnect switch the casing will be hot to the touch in several minutes.

 

[67Dart273]

Simple. There is something wrong with it. I'm not trying to be funny. Probably bad regulator.

 

[superchargeddrt]

Might be a shorted or what we call leaky diode in the alternator. If you know what you're doing it can be replaced or you can take it to a alternator repair shop. Good Luck

 

[KitCarlson]

It may be a shorted diode. The stator windings and diodes are in the case. The regulator controls the field in the rotor. It would take more minutes to get that heat to the case, the pulley might get hot first.

Did you jump a car with you engine running? That can easily fail diodes.

 

[Breadburner]

I would get it off there and to the shop......

 

[BillGrissom]

If that hot on the outside, imagine how hot on the inside. You will soon have the "burnt electrical" smell.

 

[motorhead446]

Thanks, I will get it to a shop.

 

[67Dart273]

It may be a shorted diode. The stator windings and diodes are in the case. The regulator controls the field in the rotor. It would take more minutes to get that heat to the case, the pulley might get hot first.

Did you jump a car with you engine running? That can easily fail diodes.

Dave are you aware / do you remember those STUPID "accessory devices" "they (the thems) used to sell?

These were an entirely hokey device, sometimes built into a household J box, which did the following "down the road to hell" of your alternator:

Had a various quality switch and an outlet. You would throw the switch and it:

DIS connected the output of the alternator DC from the battery and RE routed it to a common AC receptacle.

Connected "full field" 12V to the alternator.

Now what you have is a DC power outlet of various voltage, depending on how high you wind the engine, how much load you plug into it, and "whether or not" the diodes survive this mess

Parts stores used to sell these damn things.

HERE'S one NOW LMAO

(To make this very clear, these did not "convert" anything, they were a box, a switch, and an outlet)

OMFG someone actually HAS one and posted the "destructions!!"

www.hotrodders.com/forum/attachment.php?attachmentid=47836&d=1283383012

http://www.hotrodders.com/forum/e-z...nt-find-installation-instructions-117788.html

A guy HAS to wonder, just how much current that little switch will actually handle before meltage, smokeage, and burnage?

 

[KitCarlson]

Del,

Speaking of those , seems like someone sold an arc welder box.

I have been know to do things like that for experiment, but I would never sell to the public. An example is reconnecting windings in a 10 HP gasoline generator from series to parallel, then building a voltage/current exciter regulator for battery charger in my electric car. I did that in the early 80's. It worked, but was a failed experiment because it had enough noise and vibration with a one lunger, I could not concentrate enough to drive.

Diodes fail in alternators because voltage regulators do not limit alternator current. The current can be over 100A when cranking, it does not happen in a normal start, because at low speed, the alternator does not put out much. Take a running car, speed up the engine, with another car jumped, hit starter ..... diodes can go poof. Current is somewhat limited by the source impedance of alternator and associated wiring.

Back in the day before alternators, some generator systems had current limit in the voltage regulator. It could be done with alternators, but would increase cost due to current sensing.

 

[67Dart273]

Back in the day before alternators, some generator systems had current limit in the voltage regulator. It could be done with alternators, but would increase cost due to current sensing.

Actually, at least on cars and trucks MOST generators had current limiting, at least on the years they were popular. "3 unit" regulator.

You don't even need to jump a car to destroy an alternator. Just running the battery down, jumpering it to start, and then depending on the alternator to recharge the dead battery can ruin an alternator

In "the old days" of amateur radio, there was a guy, "Jo Emmett Jennings," who has made all KINDS of stuff for the RF industry, perhaps the most famous of which are very high voltage vacuum tuning capacitors, "vacuum caps." He also was one of the famous team of players for Eimac high power transmitting tubes

Jennings also did a LOT of experiments in test equipment and amateur radio gear, most notably high-power mobile gear before alternators were common.

At one time he built up a circuit in order to get high voltage DC out of the 3-phase output of an auto alternator. This then, necessarily involved 3 specially wound transformers to transform the low voltage 3 phase to high voltage, and then rectified that. It almost seems as if he used rectifier TUBES, but this was when rectifier diodes were in their infancy so he may have used them.

This was before SSB became popular and he had built a fairly high power AM transmitter in the trunk of a car, using 4CW-150 / 250 series external anode tetrodes. These were water cooled, and so did not need forced air cooling

Amazingly, I was unable to find a photo of one of them. Like below only a 'ell of a lot smaller. The entire outer metal structure where the cooling water hooks up is the anode!!! In the case of the aforementioned tubes, the anodes are operated somewhere between 1200 and perhaps 1500VDC. So water purity and connection tubing dielectric IS important LOL

(Eimac also made some tubes that were designed for "vapor phase cooling" IE cooled by the conversion of water boiling to steam and the fact that much more energy is absorbed. Part of the tube socket was actually known as a "boiler.")

 

[RustyRatRod]

It's a horny alternator.

 

[motorhead446]

Never have jumped with car or been jumped. Would put on 2amp charge between rounds sometimes when running electric fan a lot. Last night I thought my starter died only to find out my battery died. My disconnect switch is always off unless the car is running.

 

[KitCarlson]

Sounds like you are taking good care of things. If the battery failed with a cell short, the current could go high because a 10V battery can not reach the desired voltage. The regulator and alternator tries. Typically a battery short is not very low impedance, but it can be.

Large motor loads carry high current, and are inductive. When switched off, the current still wants to flow and the voltage spikes. That is seen as a reverse voltage to the diodes, if high enough they can be damaged. A way to prevent at shunt the motor with a suitable diode that is reversed biased, it will circulate the current and eliminate the spike. It is often called a freewheel diode. A good battery serves to stabilize voltage , like a huge capacitor, and actually protects the system.

If the battery has an open cell, and is running all sorts of damage can occur, especially with electronic devices. This is because regulation will be all over the place as the battery cuts in and out. Operating the battery cutoff with a running car takes careful design and considerations.

If you have a schematic for that, we can look and see if perhaps the problem is related.

 

[67Dart273]

Never have jumped with car or been jumped. .

This stuff DOES just plain fail occasionally. Are you in the habit of pulling the battery disconnect with the engine running? That, generally, is not a good plan. I've seen an alternator "load dump" but cannot remember who. A quick Google shows that several disconnects are available with this protection, but I'd bet that not all of them are high quality LOL

 

[Jay_340]

Too late for a Bruce/Caitlin Jenner tranny joke?

 

[motorhead446]

This stuff DOES just plain fail occasionally. Are you in the habit of pulling the battery disconnect with the engine running? That, generally, is not a good plan. I've seen an alternator "load dump" but cannot remember who. A quick Google shows that several disconnects are available with this protection, but I'd bet that not all of them are high quality LOL

I have used the switch to shut down car recently. I do not do it often. I mainly wanted to make sure it does what its supposed to do before going to the track.

 

[KitCarlson]

I have used the switch to shut down car recently. I do not do it often. I mainly wanted to make sure it does what its supposed to do before going to the track.

Often, is a loose term. Modern electronics is fairly predictable, exceed maximum specs parts go poof. Years ago some parts could do more, now with well controlled manufacturing parts just meet specs. For the stator to get hot, two or more diodes have failed on the 6 diode bridge.

I am guessing, but I can imagine issues related to what Del said about load dump. If the alternator is putting out current, and battery pulled from circuit, the stator inductance will kick back resulting in high voltage. If the field is powered, but the ignition cut, the regulator, seeing voltage drop would up the field, resulting in overvoltage. While some imagine opening a circuit to cut power, when inductance is involved, the cut is not immediate, and the event leads to a voltage spike. Much like ESD, a very short term event results in damage.